The present invention relates to a liquid crystal display device having a converging reflector to reflect a light from a light source to converge or condense and project the reflected light onto a predetermined plane of irradiation, and also relates to the converging reflector used for the liquid crystal display device and being capable of improving convergence efficiency.
A conventional converging reflector of one type is formed by a reflecting mirror of paraboloid of revolution wherein a light source is arranged at the focal point of the paraboloid of revolution to reflect a light from the light source to form a parallel light by the parabolic reflector.
A conventional liquid crystal display device of the type including the converging reflector of the kind described above is of a structure capable of separating a white light from the converging reflector into rays of three colors of red (R), green (G) and blue (B) by using dichroic mirrors. Respective rays of color lights of R, G and B strike on each of liquid crystal cells through condenser lenses to vary transmittance of the liquid crystal cells in response to respective image signals to thereby allow respective rays of incident color lights of R, G and B to be transmitted therethrough or intercepted thereby, thus projecting images corresponding thereto onto a screen through a projection lens.
Since the conventional converging reflector is constructed as described above, a light source which can be considered as a point light source must be arranged at the focal point of the reflecting mirror in order to permit a light to be reflected on an ideal circular plane of projection or an ideal point.
However, the point light source cannot get high luminance or brightness. Hence, for example, a metal halide lamp is used as a lamp having a high luminance and a long life span. A light is emitted between two electrodes in the metal halide lamp. For this reason, such a light source cannot be considered as the point light source and the size of that light source would not be negligible, thus disadvantageously failing to allow a light to be reflected to an ideal circular shape or an ideal point on a plane of projection. Hence, the converging reflector is not capable of improving convergence efficiency.
The convergence efficiency of the liquid crystal display device using the converging reflector is an illuminance of rays which is reflected on the converging reflector and then pass through the condenser lens, liquid crystal cell and projection lens.
In the case of the conventional liquid crystal display device, although an incident light from the converging reflector is projected through the dichroic mirrors, the condenser lenses, the liquid crystal cells, and the projection lens, only each of the convergence efficiencies of the converging reflector and liquid crystal cell is taken into consideration, but the correlation of the entirety of the liquid crystal display device is not taken into consideration by any means. Thus, the convergence efficiency of the entirety of the liquid crystal display device is unable to be improved.